Where 2 straight edges meet at a corner, the shortest distance around that corner is an arc (with the center on the corner). As well as the distance being less than say carrying on past the corner then stop, 90 turn then start off again. Imagine going down the freeway and in order to take a turn off, you pull on the hand break, slide sideways then wait to stop before flooring it to head off in the other direction. Entertaining yes, but it's not the most efficient way of driving your machine. With arcs, while one motor is slowly decelerating, the other is accelerating. Arcs sound nicer! If your driver and controller are setup, a series of arc toolpaths just sounds nice and smooth. Lots of straight segments sounds very juddery. Then there is the actual cutting business. Driving a cutter into a 90 degree bend can be rather unpleasant. I am not a machinist (IANAM), but I think curved cutting paths are more efficient and kinder on your cutters.
If you really really don't want to do ANY arcs, then you can set the ArcOutput machining option to ConvertToLines, but as it suggests the many short segments may cause jittering with TNC.
With the MinArcLength, i think at a certain point, the min arc length is too big, it needs to replace the 90 degree arcs with a straight line, which it can't do as this would end up cutting the corner. MinArcLength is more useful to avoid those small glitches where filler arcs are used at a size which upsets the interpreter.
Have you tested your driver setup? Sometimes things like a motor step signal that needs inverting can cause odd behaviour. Is your motor tuning OK? Is acceleration and deceleration sensible? You should be able to get your machine moving in a nice smooth circles using arc moves, if not somethings up. Good Luck!
